1. Field of the Invention
This invention relates to motors and/or actuators. In particular, there is a two-phase electro-mechanical stepper motor having 1) a high ratio of torque per mass and torque per power draw, to be able to develop required rotating torque, 2) a magnetic circuit that allows developing of a significant holding torque while using a limited amount of electric power, and 3) two disk stators with salient poles are positioned on either side of two disk rotors and 4) a gear train positioned between the rotors.
2. Description of the Related Art
Various devices dealing with stepper motors are legion. Examples of patents related to the present invention are as follows, and each patent is herein incorporated by reference for the supporting teachings:
U.S. Pat. No. 5,512,871 is a rotatable single phase electromagnetic actuator.
U.S. Pat. No. 5,334,893 is a monophase electromagnetic rotary actuator of travel between 60 and 120 degrees.
U.S. Pat. No. 5,298,825 is a single phase electromagnetic actuator with low obstruction.
U.S. Pat. No. 5,054,940 is a ceramic bearing design for attachment to a shaft.
U.S. Pat. No. 4,973,866 is a variable angle stepper motor.
U.S. Pat. No. 4,645,430 is a wet motor fuel pump with self aligning bearing.
U.S. Pat. No. 3,749,458 is a centering device for a rotary shaft.
WIPO PCT patent publication 99/13558 is a brushless DC motor.
The foregoing patents reflect the state of the art of which the applicant is aware and are tendered with the view toward discharging applicants' acknowledged duty of candor in disclosing information that may be pertinent in the examination of this application. It is respectfully stipulated, however, that none of these patents teach or render obvious, singly or when considered in combination, applicant's claimed invention.
Referring to FIG. 1, there is a cross section of a typical related art rotatable single phase electromagnetic actuator 10. Actuator 10 has a shaft 12 with an axis 13, a stator 14, a rotor 16, and a bearing structure 25. The stator has a magnetic field inducing wire coil 18, a stator pole shoe 20, and a bearing support 24. Bearing assembly 25 includes a top and bottom bearing retaining housing 26, and a plurality of ball bearings 28. The rotor 16 includes a set of rotor magnets 22. Other supporting structures such as a housing and other bearings have been omitted for clarity. It is noted that the actuator illustrates an ideal design, where the bearing parts, stator parts and rotor parts have all respective surfaces appropriately aligned either perpendicular or parallel.
3. Problem with the Related Art
A common problem occurring with multi-position valves is that they require a driving actuator that both 1) develops a significant rotating torque to move from one angular position to another, and 2) can be locked in one of the angular positions, usually by a holding torque. Both competing needs must be met without using large amounts of electric power.
Some specific applications may require more torque than the actuator can provide. A solution to this problem is to add a gear train to an end of the actuator. However, in some applications space constraints may preclude this.
Therefore, there is a need for a stepper motor that both steps to various positions and holds at those positions with low power usage. Additionally, there is a need for a motor that has a poly-phase electric power supply to enable a switch to turn on or off the power to parts of its winding and, for example, reverse the direction of rotation, and there is a need for a motor with an integrated gear train for applications with even higher torque requirements.